IGBTs are well known. IGBTs can be designed for punch through or non-punch through operation. A known IGBT structure and process for its manufacture for IGBTs used for motor control application employ a non-punch through (NPT) mode of operation in which the device is designed to have a low forward voltage drop (VCEON) when the device is conducting, at the expense of an increased turn off energy (EOFF).
Such devices are not well adapted to application to switch mode power supplies in which the turn off energy EOFF is to be minimized, even at the expense of a higher VCEON.
It would be very desirable to provide a process to produce high voltage (eg. 600 volts) NPT IGBTs with a reduced EOFF which do not require substantial process changes over those normally used for conventional IGBT.